Bilayer windshield and preformed two-ply sheet for use therein

ABSTRACT

Preformed, two-ply, optical, energy-absorbing, flexible polyurethane sheet including a self-healing surface and a surface which is adhesive under the influence of heat and pressure; bilayer glazing laminates and bilayer automotive safety windshields including said two-ply sheet; said two-ply sheet comprises a self-healing ply and an energy-absorbing adhesive polyurethane ply which is prepared preferably by reactive-casting on a horizontal support and formed preferably from a polyisocyanate monomer including from about 2 to about 10 wt. % of urea groups.

This application is a continuation, of application Ser. No. 06/629,370,filed July 10, 1984, now abandoned.

FIELD OF THE INVENTION

The present invention relates to a preformed two-ply plastic sheethaving energy-absorbing, adhesive, and scratch resistant properties, andto a glazing laminate including said sheet and methods and compositionsuseful for the preparation of said sheet and laminate. This inventionrelates also to a bilayer laminate having improved moisture resistant,energy-absorbing, optical and scratch resistant properties and, inparticular, to an improved vehicle windshield including an inner exposedply of scratch resistant, anti-lacerative, self-healing plasticmaterial.

Reported Developments

The patent literature extending over a period of almost half a centuryreveals numerous efforts to fabricate a bilayer laminate which is usefulas a vehicle safety windshield and which comprises a single ply of glassand a ply of energy-absorbing, mar-resistant plastic material. That theproducts of such attempts have not been entirely satisfactory isevidenced by the present unavailability of a commercially acceptablebilayer windshield.

Bilayer laminates are disclosed in U.S. Pat. Nos. 3,808,077; 3,881,043;3,900,686; 4,041,208; 4,085,092; 4,109,055; 4,139,764; and 4,039,720;and in the following copending U.S. applications, each of which isassigned to the same assignee as the present application, U.S. Ser. Nos.213,225, now U.S. Pat. No. 4,623,592; 274,547, abandoned; and 579,035,now U.S. Pat. No. 4,584,229. Invariably the plastic ply of the bilayerlaminates disclosed therein have one or more desirable properties, suchas energy absorption, optical clarity, or chemical resistance, but areeither impractical to manufacture and/or deficient in one or more otherproperties, such as, for example, adhesive strength, mar-resistance, ormoisture sensitivity. For example, bilayer laminates comprising a singleplastic ply having acceptable scratch resistant properties suffer from adecided lack of energy-absorbing and adhesive properties, while thosebilayer laminates having acceptable energy-absorbing properties sufferfrom a decided lack of scratch resistance and a lack of adhesiveproperties. The prior art has dealt with some of these shortcomings suchas insufficient adhesive strength by utilizing an adhesion promoter orseparate adhesive layer, while the deficiencies such as inadequatescratch resistance have been approached by providing a separate surfacetreatment such as a hard or soft scratch resistant coating or byproviding a two-ply plastic sheet which combines the desirableproperties of two materials in one ply. However, these approaches havealso encountered problems, such as deficiencies in one or more otherproperties including optical clarity.

Many plastics, including polyvinyls, polycarbonates, and polyurethanes,have been proposed for use in bilayer laminates. Polyurethanes have beenwidely used as both an exposed ply and as an interlayer sandwichedbetween two sheets of glass or plastic. Various types of polyurethaneshave been described for such glazing uses in the patents andapplications mentioned above, as well as in U.S. Pat. Nos. 3,509,015,3,620,905, and 4,241,140, but they do not possess to the desired extentall of the properties that are needed in a plastic sheet for use in asuccessful bilayer windshield.

The present invention relates to an improved polyurethane sheet which isparticularly useful for preparing a bilayer glazing laminate as theresult of its possessing a combination of properties that are requiredin this type of safety product.

SUMMARY OF THE INVENTION

The present invention relates to a preformed transparent two-ply sheethaving optical properties and comprising a self-healing ply and anenergy-absorbing polyurethane ply, characterized in that saidpolyurethane ply is prepared by reactive casting on a level, horizontalsupport, a reaction mixture including: an isocyanate component, having aviscosity of less than 5000 mPaS at 40° C., and comprising an aliphaticdiisocyanate, a cycloaliphatic diisocyanate or an isocyanate prepolymer;and, a polyol component comprising a polymeric diol having a molecularweight (hereinafter "MW") of about 500 to about 4000, and a short chaindiol.

The present invention relates also to a preformed flexible multi-plytransparent sheet, effective for use in a bilayer glazing laminate,having optical, moisture resistant, and energy-absorbing propertieseffective for use in a bilayer glazing laminate, one ply of whichcomprises a self-healing thermoset polymeric material, the other ply ofwhich comprises an energy-absorbing polyurethane ply which issubstantially non-tacky at room temperature but which is capable ofitself being adhesive under the influence of heat and pressure, saidsheet characterized in that, as an exposed ply in a glazing laminate, itis capable of maintaining, in the absence of an adhesion promoter,effective adhesion as measured by the temperature and moistureconditions of Test Nos. 3 and 4, American Standard Safety Code forSafety Glazing Materials for Glazing Motor Vehicles Operating on LandHighways, Revision Z26.1 - 1966 (hereinafter "ANSI-Z26").

This invention relates also to a method for the preparation of apreformed flexible, transparent multi-ply polyurethane sheet of the typedescribed above comprising:

(1) depositing on a horizontal support a liquid film comprising asolvent-free mixture of monomers capable of forming a thermosetpolymeric material;

(2) forming a solid underlying film of thermoset polymeric material bypolymerizing said monomers while on said support;

(3) depositing on said supported underlying film a liquid filmcomprising a solvent-free mixture of monomers capable of forming anenergy-absorbing polyurethane ply and a polyurethane forming catalyst;

(4) forming a solid, optical, energy-absorbing overlying polyurethaneply within about an hour, thereby forming said multi-ply sheet; and

(5) removing said multi-ply sheet from said support.

A further aspect of the present invention relates to a bilayer glazinglaminate which exhibits optical, energy-absorbing, moisture andtemperature resistant, and abrasion resistant properties as required byANSI Z26, Test Nos. 1-4, 9, 12, 15-19, 24, 26 and 28, comprising amulti-ply preformed sheet as described above adhered to a glass orplastic ply.

Another aspect of the present invention relates to a bilayer safetywindshield comprising the present multi-ply preformed sheet adhered to aglass ply and which complies with the testing requirements of 49 CFR571.205 (S5.1.2.3) [as amended Nov. 16, 1983].

Other aspects of the present invention, including methods for thepreparation of glazing laminates, are described herein.

DETAILED DESCRIPTION OF THE INVENTION

The term "adhesion promoter" means a material which, when added to apolyurethane solution or to the reaction mixture from which thepolyurethane is prepared, or when used to coat the surface of apolyurethane article, improves the strength and longevity of an adhesivebond including said polyurethane. Exemplary adhesion promoters includealkoxy silanes such as: gamma aminopropyl-triethoxysilane, sold as"A-1100" by Union Carbide Corp. or by Dow Corning as "Z-6020"; andN-(beta-amino ethyl) gamma aminopropyl-trimethoxysilane sold by UnionCarbide Corp. as "A-1120." Adhesion promoters are disclosed also in U.S.Pat. No. 3,881,043.

The sheet of the present invention possesses exceptional adhesiveproperties of the type required in a safety windshield in the absence ofthe use of an adhesion promoter. However, it should be understood thatan adhesion promoter may be used in the practice of the presentinvention for reasons which are independent of the inherent adhesiveproperties possessed by the sheet invention. For example, an adhesionpromoter can be used to compensate for a decrease in sheet adhesion dueto the presence of an adhesion inhibitor such as a silicone flowenhancing agent, or to improve the adhesive properties of the sheet in amanner such that they exceed the present industry safety standards forthe adhesive requirements of a glazing laminate.

The surface of the energy-absorbing ply of the present sheet issubstantially non-tacky at room temperature (for example, about 15° C.to about 35° C.), that is, at temperatures likely to be encountered in afacility in which the sheet is manufactured, stored, and/or used inpreparing a glazing laminate. At temperatures in excess of about 35° C.,its adhesive surface is softened to the extent that when the sheet ispressed to a glass or plastic substrate, it is capable of flowing andadhering to the substrate to an extent that the sheet does not slip orslide on the surface of the substrate. Treatment of the assemblyresulting from the sheet and substrate at elevated temperature andpressure forms a laminate comprising an exposed ply of the presentsheet. The adhesive bond formed by the sheet to the underlying ply ofthe laminate maintains its bond, even in the absence of the use of anadhesion promoter, under adverse temperature and humidity conditions, asevaluated in ANSI Z26 Test Nos. 3 and 4, described in detail below.

The exceptional nature of the adhesive bond of the sheet, as well as theenergy-absorbing, optical and other properties of the sheet andlaminates according to the present invention may be evaluated accordingto standard tests published by the American Standards Association inAmerican Standard Safety Code for Safety Glazing Materials for GlazingMotor Vehicles Operating on Land Highways, Revision Z26.1-1966("ANSI-Z26") and according to tests published in Addendum 42: RegulationNo. 43 of the "United Nations Agreement Concerning the Adoption ofUniform Conditions of Approval and Reciprocal Recognition of Approvalfor Motor Vehicle Equipment and Parts" (hereinafter "ECE R43"), herebyincorporated by reference.

The temperature and moisture resistance of the present laminates may beevaluated by the ANSI-Z26 Humidity and Boil test procedures, reproducedbelow.

Humidity, Test No. 3

5.3.1 Purpose of Test

The purpose of this test is to determine whether the safety glass willsuccessfully withstand the effect of moisture in the atmosphere over anextended period of time.

5.3.2 Procedure

Three 12×12-inch flat specimens, as submitted, shall be kept for 2 weeksin a closed container over water. The temperature of the air in thecontainer shall be maintained within the limits of 120° and 130° F.(These conditions give a relative humidity of about 100 percent.)

5.3.3. Interpretation of Results

No separation of materials shall develop, except for occasional smallspots, no one of which shall extend inward from the adjacent edge of thespecimen to a depth of more than 1/4 inch.

Boil, Test No. 4 (this test is not applicable to multiple glazed units.)

5.4.1 Purpose of Test

The purpose of this test is to determine whether the safety glass wilsuccessfully withstand exposure to tropical temperatures over anextended period of time.

5.4.2 Procedure

Three 12×12-inch flat specimens, as submitted, shall be immersed,vertically on edge, in water at 150° F. for 3 minutes and then quicklytransferred to and similarly immersed in boiling water. The specimensshall be kept in the boiling water for 2 hours and then removed.

5.4.3. Interpretation of Results

The glass itself may crack in this test, but no bubbles or other defectsshall develop more than 1/2 inch from the outer edge of the specimen orfrom any cracks that may develop. Any specimen in which the glass cracksto an extent confusing the results shall be discarded without prejudiceand another specimen shall be tested in its stead.

The laminates of the present invention both prepared with and without anadhesion promoter additive, pass ANSI-Z26 Test Nos. 3 and 4.

The energy-absorbing, adhesive ply of the sheet within the scope of thepresent invention can be prepared from a reaction mixture comprising apolyisocyanate component, a polymeric polyol and a low molecular weightdiol. A preferred embodiment of the present invention comprises anadhesive polyurethane ply formed from a reaction mixture including apolyisocyanate monomer component containing about 2 to about 10 wt. % ofurea groups.

The polyurethane-forming components are present in the reaction mixturesuch that the molar ratio of the available NCO groups to available OHgroups is about 0.8:1 to about 1:1. As the NCO/OH ratio becomes greaterthan one, for example, about 1.01:1 to about 1.1:1, the sheet becomesmore rigid. When the polyurethane forming monomers are all difunctional,the NCO/OH ratio is preferably 0.9:1 to 1:1, and most preferably theratio is about 1:1.

The polyisocyanate component comprises an aliphatic, cycloaliphatic orprepolymer polyisocyanate and preferably a diisocyanate. Exemplarydiisocyanates include: 1,6-hexamethylene diisocyanate (HMDI);2,2,4-trimethyl-1,6-hexane diisocyanate (TMDI);bis(4-isocyanatocyclohexyl)methane in any number of differing isomericratios, preferably the isomeric mixture sold as "Hylene W";bis(3-methyl-4-isocyanatocyclohexyl)methane;2,2-bis(4-isocyanatocyclohexyl)propane;3-isocya-natomethyl-3,5,5-trimethylcyclohexy referred to also asisophorone diisocyanate or IPDI; transcyclohexane-1,4-diisocyanate;m-xylylene diisocyanate; m- and p-tetramethylxylylene diisocyanate; and1,3-(diisocyanatomethyl)cyclohexane.

As mentioned above, a preferred polyisocyanate component includes about2 to about 10 wt. % of urea groups, more preferably about 5 to about 7wt. % of urea groups. A particularly preferred polyisocyanate componentcomprises a cycloaliphatic diisocyanate including about 5 to about 7 wt.% of urea groups and is most preferably a urea-modified isophoronediisocyanate comprising a mixture of isophorone diisocyanate and theurea-containing diisocyanate adduct of isophorone diisocyanate andwater, such as N,N'-bis(isophorone isocyanato)urea, and in which the NCOcontent of the mixture is about 30 to about 33 wt. %. A most preferredurea-containing polyisocyanate monomer component comprises a mixture ofisophorone diisocyanate, "IPDI", and the urea-containing IPDI product,"IPDI H-2921", each product sold by Huls Co.

The polymeric polyol component comprises a polyether diol or polyesterdiolhaving a MW of about 500 to about 4000. Exemplary polyester diolsinclude: polylactone diols, for example, polycaprolactone diol; and, theesterification products of a diacid and a low molecular weight diol.Exemplary diacids are adipic, succinic, palmitic, azelaic, sebacic andphthalic acid. Exemplary low molecular weight diols are ethylene glycol,propane-1,3-diol, butane-1,4-diol, and hexane-1,6-diol. Exemplarypolyether diols include those described by the linear chain formulaH--[O(CH₂)_(n) ]_(m) OH, where n is about 2 to about 6, and the branchedchain formula ##STR1## where, in both formulae, m is such that the MW ofthe polymer is about 500 to about 4000. A portion of the polyolcomponent may be replaced with a polyamine monomer.

The preferred polymeric polyol comprises a polyether diol, and mostpreferably polytetramethylene glycol having a molecular weight of about1000.

Exemplary short chain diols for use as chain extenders have a MW of lessthan about 300 and preferably a MW less than about 150 and include:ethylene glycol; propane-1,2-diol; propane-1,3-diol; butane-1,2, -1,3,or -1,4-diol; dimethyl-2,2-propane-1,3-diol (neopentylglycol);pentane-1,5-diol; hexane-1,6-diol; octane-1,8-diol; decane-1,10-diol;dodecane-1,12-diol; cyclohexanedimethanol; bisphenol A;2-methylpentane-2,4-diol; 3-methylpentane-2,4-diol;2-ethylhexane-1,3-diol; 2,2,4-trimethylpentane-1,3-diol;diethyleneglycol; triethyleneglycol; tetraethyleneglycol;2-butyne-1,4-diol; butene-1.4-diol; decynediol; substituted and/oretherified, hydroquinone-bis-hydroxyethylether; bisphenol A, etherifiedby two or four groups of propylene oxide; or dimethylolproponic acid.The most preferred short chain diol for use as a chain extender isbutane-1,4-diol.

The molar ratio of polymeric diol to chain extender diol may beexpressed in terms of an OH equivalent ratio and varies as a function ofthe properties desired in the polyurethane sheet. The molar ratio ofpolymeric diol to chain extender diol is about 0.3:1 to about 1:1. Asthe percentage of chain extender diol is increased, the resultingpolyurethane ply may harden and its modulus of elasticity increase.

A particularly preferred embodiment of the present invention comprises apolyurethane sheet wherein the adhesive ply is formed from a monomermixture including a small amount of tri- or higher functional monomers,such as, a polyisocyanate component including less than about 15 NCOequivalent percent of a triisocyanate such as a biuret or atriisocyanurate; or a polyol component including a small amount of apolyol having a hydroxy functionality greater than two and,particularly, a polyol component such as an aliphatic polyol, forexample, glycerol, trimethylolpropane, or a polyether or a polylactonepolyol, having a functionality greater than two, such as a triol, andhaving a MW of about 90 to about 1000. An exemplary polyol includes apolypropylene glycol ester of a mixture of dimerized and trimerizedlinolenic acid, having an OH functionality between 2 and 3. A mostpreferred aliphatic polyol is a polymeric triol which most preferablycomprises polycaprolactone triol. A polyurethane sheet wherein theadhesive ply is prepared from a composition including a monomer otherthan a diol or diisocyanate exhibits improved cohesive properties.

The OH-equivalent ratio of the polyol of functionality greater than two(hereinafted referred to as the "triol") relative to the polymeric dioland chain extender diol can vary. The polymeric diol comprises about 30to about 45 OH equivalent percent of the total OH content in thepolyurethane-forming reaction mixture; the chain extender diol comprisesabout 20 to about 70 OH equivalent percent; and, the triol comprises upto about 35 OH equivalent percent, such as between about 0.05 and about35 OH equivalent percent. A preferred molar ratio of polymeric diol totriol is about 1.5:1 to about 4:1, and that of polymeric diol to chainextender diol is about 0.5:1 to about 0.8:1.

A particularly preferred embodiment of the present invention comprises apolyurethane sheet formed by "reactive casting", a term used herein torefer to a process in which a liquid film comprising a monomericreaction mixture is formed on a horizontal support and a solid fullycured polymeric sheet prepared by polymerizing the reaction mixture inthe form of the liquid film at a temperature (for example, between about80° to about 140° C., and preferably about 100° to about 140° C.) andwithin a time period practical for use in a continuous industrialprocess. The two-ply sheet can be formed by reactive casting whereineither the thermoset or adhesive, energy-absorbing ply is formed first.A preferred embodiment of the present invention comprises a preformedtwo-ply sheet, one surface of which comprises a self-healing thermosetpolymeric material, the other surface of which comprises the reactivecast polyurethane, and which is prepared by:

(1) forming on a horizontal support a liquid film comprising a mixtureof monomers capable of forming a thermoset polymeric material;

(2) polymerizing said liquid film thereby forming a solid underlyingsupported ply;

(3) forming on said supported ply an overlying liquid film comprising asolvent-free mixture of monomers capable of forming a polyurethane and apolyurethane-forming catalyst;

(4) maintaining the temperature of said overlying film for a timesufficient to permit the formation of a uniformly thick and level liquidfilm;

(5) raising the temperature of said level liquid film and maintaining anelevated temperature sufficient to fully polymerize said film and forman overlying solid polyurethane film in less than about an hour, therebyresulting in a supported multi-ply sheet; and

(6) removing said multi-ply sheet from said support.

A particularly preferred means for preparing the present sheet comprisesraising the temperature of the uniformly thick and level film to saidelevated temperature within a minimal time period such as less thanabout 3 minutes, and polymerizing the liquid film in less than about 30minutes. The term "uniformly thick and level liquid film" describes afilm which has a uniform thickness on a level support such that a solidfilm prepared therefrom has optical properties acceptable for glazingapplications.

A particularly preferred polyurethane for use in preparing the overlyingpolyurethane ply according to the present invention by reactive casting,as described above, is formed from:

(A) a cycloaliphatic polyisocyanate component including about 2 to about10 wt. % urea groups and about 30 to about 33 wt. % of NCO groups;

(B) a polyol component including:

(1) about 30 to about 45 OH equivalent percent of a polymeric diolhaving a MW of about 500 to about 3000;

(2) about 20 to about 70 OH equivalent percent of a chain extender diol;and

(3) about 0 to about 35 OH equivalent percent of a triol; and

(C) a polyurethane-forming catalyst;

wherein the NCO/OH ratio of said mixture is about 0.8:1 to about 1:1.

Exemplary polyurethane forming catalysts are: a tin catalyst, forexample, dibutyltin dilaurate, tributyltin oxide, tin octoate; anorganomercuric catalyst, for example, mercuric phenyl ester; and anamino catalyst, for example, diazabicyclo-(2,2,2)-octane, and1,8-diazabicyclo(5,4,0)-1-decene-7. A tin catalyst is preferred in anamount comprising greater than about 0.01 to about 0.05 weight percentbased on the total weight of the liquid film composition.

The composition forming the present sheet can also include a stabilizersuch as bis(2,2,6,6-tetramethyl-4-piperidyl) sebecate or a phenolicantioxidant, and a sheeting or flow enhancing agent such as afluoroalkylated ester, an acrylic resin, or a silicone resin. Afluoroalkylated ester sheeting agent is preferred.

In a most preferred form, the above composition has a viscosity suchthat the liquid film formed therefrom attains a uniformly thick andlevel form on the horizontal support within about 0.5 to about 5minutes.

A preferred horizontal support has a surface which is smooth, level anddefect-free and renders the film formed thereon with a correspondingoptically defect-free surface. A most preferred horizontal supportcomprises a release surface such as a supported Teflon material or thelike or a support coated with a release agent such as a modifiedaddition product of ethylene oxide of the formula

    R.sub.1 --X--(C.sub.2 H.sub.4 O).sub.n --R.sub.2

in which:

R₁ represents an alkyl group containing about 8 to about 18 carbon atomsor an alkyl-aryl group containing about 6 to about 12 carbon atoms inthe alkyl chain;

R₂ represents one of the following groups:

PO₃ M₂

CO--CH(SO₃ M)--CH₂ COOM

CO--C₆ H₄ --COOM

M is an alkali metal and

X represents one of the following groupings:

O, CO--O or CO--NH and

n is about 1 to about 100.

The most preferred release agent in the practice of the presentinvention is a disodium polyether sulfosuccinate as disclosed in U.S.Pat. No. 4,331,736.

The polyurethane sheet prepared as described above may be removed fromthe horizontal support and stored for later use or used immediately toform a glazing laminate as described herein below. A particular aspectof the present method relates to a sheet wherein the preferred adhesivesurface is formed opposite that surface formed in contact with thehorizontal support. Another aspect of the present method relates to theimproved surface characteristics, such as the scratch and abrasionresistant properties, exhibited by the surface formed in contact withthe horizontal release support.

The reactive cast adhesive and energy-absorbing polyurethane plypossesses both thermoplastic- and thermoset-type properties. Forexample, it has thermoset-type properties in that it is infusible andinsoluble in most polyurethane solvents such as tetrahydrofuran anddimethylformamide, and it exhibits thermoplastic-type properties in thatit softens and adheres at elevated temperatures. Furthermore, thereactive cast sheet exhibits surprising energy-absorbing properties.Although applicants do not wish to be bound by any particular theory, itis believed that the temperature, catalyst concentration, NCO/OH ratioand other parameters of reactive casting promote the formation ofsecondary chemical branching such as the formation of allophanate and/orbiuret linkages, and that this secondary branching is, in part,responsible for the properties of the present sheet. Furthermore, itshould be noted that when the NCO/OH ratio is less than about 1:1 andthe polyurethane forming monomer components are difunctional in nature,the secondary branching described above does not occur to anysignificant extent and the energy-absorbing properties are reduced.

In a most preferred embodiment of the present invention, the presentreactive cast energy-absorbing ply exhibits the following mechanicalproperties, measured according to AFNOR/NFT standard 46 002, 51 034 and54 108:

a tensile strength at 10 percent elongation, σy at -20° C. less than orequal to about 300 daN/cm² ;

a tensile strength at break, σR at +40° C. greater than or equal toabout 200 daN/cm² ;

an elongation to rupture εR at +20° C. ranging from about 250 to about500 percent; and

an initial tear strength Ra at +20° C. with a thickness greater than orequal to about 90 daN/cm.

As mentioned above, one ply of the present two-ply sheet comprises aself-healing, thermoset polymeric material and the other ply comprisesthe energy absorbing, adhesive polyurethane described hereinabove. Apreferred self-healing material exhibits properties such that, undernormal temperature conditions, the self-healing ply has a high capacityfor elastic deformation, a low modulus of elasticity, less than 2000daN/cm² and preferably less than 200 daN/cm², and an elongation atbreaking of more than 60 percent with less than 2 percent plasticdeformation and preferably an elongation at breaking of more than 100percent with less than 1 percent plastic deformation. The preferredfilms of this type are thermoset polyurethanes with a modulus ofelasticity of about 25 to 200 daN/cm² and an elongation of about 100 to200 percent with less than 1 percent plastic deformation.

Examples of polyisocyanates suitable for the preparation of thesethermoset polyurethanes include: 1,6-hexane-diisocyanate;2,2,4-trimethyl-1,6-hexanediisocyanate;2,4,4-trimethyl-1,6-hexanediisocyanate;1,3-bis(isocyanatomethyl)benzene; bis(4-isocyanatocyclohexyl)methane;bis(3-methyl-4-isocyanatocyclohexyl)methane;2,2-bis(4-isocyanatocyclohexyl)propane; and3-isocyanatomethyl-3,5,5-trimethyl-cyclohexylisocyanate; and thebiurets, isocyanurates and NCO prepolymers thereof. Examples of polyolssuitable for the preparation of the thermoset polyurethanes includestraight-chained and branched polyols, such as the following: thepolyesterpolyols and the polyetherpolyols obtained by reaction ofpolyfunctional alcohols such as 1,2,3-propanetriol(glycerol);2,2-bis(hydroxymethyl)-1-propanol(trimethylolethane);2,2-bis(hydroxymethyl)-1-butanol(trimethylolpropane);1,2,4-butane-triol; 1,2,6-hexane-triol;2,2-bis(hydroxymethyl)-1,3-propane-diol(pentaerythritol); and1,2,3,4,5-5-hexane-hexol(sorbitol); with either the aliphatic diacidssuch as malonic acid; succinic acid; glutaric acid; adipic acid; subericacid; and sebacic acid; or with the cyclic ethers, such as ethyleneoxide; 1,2-propylene oxide and tetrahydrofuran.

The molecular weight of the polyols is about 250 to about 4000 andpreferably is about 450 to about 2000. Mixtures of differentpolyisocyanate and polyol monomers can be used. An especially preferredthermoset polyurethane is the one disclosed in U.S. Pat. Nos. 3,979,548and 4,232,080.

The thickness of the present two-ply sheet can be varied depending onthe use of the sheet. It is believed that a great many applications ofuse will be served satisfactorily by a sheet thickness of about 0.1 toabout 1.0 mm, and preferably greater than about 0.5 mm. In such sheets,the energy-absorbing ply is about 0.1 to about 0.8 mm thick. In glazinglaminate applications where impact resistance and energy-absorbingproperties of the sheet are desired, the energy-absorbing ply ispreferably greater than about 0.4 mm thick.

The present sheet may be utilized in a variety of laminate applications,including lenses, windows or transparencies for use in the optical,building, transportation and security industries, such asbullet-resistant windows or partitions, and side or lateral windows inmotor vehicles, planes and trains. Additionally, the present sheet maybe laminated to a container, for example, glass or plastic bottles. Thepresent invention particularly relates to a bilayer glazing laminatecomprising a single sheet of glass or a rigid plastic substrate and thepresent preformed sheet. A glazing laminate of particular interest is avehicle windshield comprising an outer-glass ply and an inner ply ofpolyurethane.

The glass ply which can be employed in the laminates of the presentinvention can be of any type, depending upon the intended use of thelaminate, but preferably is a clear, low-colored, transparent type ofglass, such as the well-known silica glass, particularlysoda-lime-silica glass. The nature and composition of various sodaglasses is known in the art and is described, for example, in theEncyclopedia of Chemical Technology, by Kirk-Othmer, published byInterscience Encyclopedia Inc., New York, N.Y., Vol. 7, pages 181-189.The glass can be strengthened by either thermal or chemical tempering.

The thickness of the glass can vary depending on the ultimate end use.Typically, the glass can have a thickness of from 50 to 500 mils (0.127to 1.27 cm). For automobile and other motor vehicle window uses, theglass will preferably have a thickness between about 65 and 180 mils(0.165 and 0.457 cm), and most preferably about 3.0 mm.

Besides glass, other rigid transparent sheets, such as polycarbonate andacrylic sheeting, can be used to form the laminates of the presentinvention. Also, besides bilayer laminates, the polyurethane interlayersof the present invention can be used to make tri- and multi-plylaminates in which the sheet of the present invention may be interposedbetween alternating rigid transparent sheets (e.g., glass, polycarbonateor acrylic). Also, the polyurethane sheet of the present invention canbe used in combination as a flexible ply between alternating layers ofrigid transparent sheet in combination with other flexible plastic pliessuch as polyvinyl butyral. Such multi-ply laminates are useful asaircraft transparencies or as bullet-proof glass for armored vehicles.

Another aspect of the present invention relates to a method forpreparing a glazing laminate comprising:

(1) providing a preformed polyurethane sheet formed on a horizontalsupport, according to the method described above.

(2) removing said solid polyurethane sheet from said horizontal support;

(3) contacting a glass or plastic ply surface with the surface of saidsheet opposite that formed in contact with said horizontal support,thereby forming an assembly; and

(4) treating said assembly at elevated temperature and pressure.

In preparing a glazing laminate, the present preformed sheet can beassembled by using pressure and/or heat and is preferably contacted witha rigid plastic or glass ply under pressure, for example, by pinchingbetween the rollers of a calenderer. The adhesive bond may be improvedby subjecting the aforesaid assembly to an autoclaving cycle, forexample, for about one to about two hours at a temperature of about 100°C. to about 140° C. and a pressure of about 3 to about 15 bars. A bakingcycle may be used in place of an autoclaving cycle.

The adhesive strength of the laminates of the present invention may bemeasured by the 90 degree angle peel test described in NASA Tech Brief65-10173. A 5 cm wide strip of laminate is adhered to a pull bar and aseparating force applied to the laminate at a 90° angle and adjusted toresult in separation of the laminate at a rate of 5 cm/min. The adhesiveforce needed to separate the laminate is reported hereinbelow in unitsof decanewtons (daN) per 5 linear cm.

The degree of adhesion in bilayer glass laminates of the presentinvention is recommended to be about 2 daN/5 cm to about 15 daN/5 cm,preferably about about 3 daN/5 cm to about 11 daN/5 cm. This adhesion islow enough to allow sufficient polyurethane ply to release from theglass ply so that it can stretch without tearing to absorb impactingenergy, yet the degree of adhesion is sufficient for retention of brokenglass. Higher degrees of adhesion, that is, much higher than about 15daN/5 cm can result in decreases in impact resistance, described in moredetail below. Lower degrees of adhesion, that is, lower than about 2daN/5 cm are insufficient for commercial vehicle use in thatdelamination may occur, particularly under high humidity conditions.

Furthermore, the degree of adhesion in the present laminate should berelatively stable over a wide range of temperature and humidityconditions. By relatively stable under a wide range of temperature andhumidity conditions is meant that although there may be fluctuations inthe adhesive value over a period of time, the degree of adhesion remainswithin the range described above.

A particularly preferred embodiment of the present invention relates toa bilayer glazing laminate which exhibits energy-absorbing, optical,moisture resistant, and abrasion resistant properties in compliance withU.S. and European automotive safety regulations, and, in particular,ANSI-Z26 and ECE R43 standards. In addition to the properties measurableby the aforesaid standards, glazing laminates prepared from the presentsheet exhibit self-healing properties. These properties may be evaluatedby the Erichsen Test described below.

Scratch resistance--Scratch resistance may be measured by the ErichsenType 413 tester equipped with a diamond stylus having a tip radius of 15microns and an included angle of 50°. A sample of the sheet to be testedis adhered to a substrate such as glass, which is rotated duringtesting. The diamond stylus is placed on top of the surface to be testedand is attached to a calibrated arm which permits a weight of from 0 to100 grams to be exerted through the stylus. The laminated sheet isrotated during testing and the highest value (in grams) determined atwhich the sheet is not permanently deformed by tearing.

Sheets of the present invention exhibit scratch resistance that isgreater than about 20 g and the property of recovery after deformation,meaning that a deformation in the surface of the present sheet willdisappear or recover within a period of time of less than about tenminutes.

The following test procedures are used to determine the abrasionresistance, and impact resistance of bilayer laminates of the presentinvention.

Abrasion resistance--Abrasion resistance may be determined according toANSI-Z26 Test No. 17, as applicable to bilayer glass-plastic laminatesin according with 49 CFR §571.205, S.5.1.2.3 (as amended Nov. 16, 1983)(corresponding to Test No. 4, ECE R43), portions of which are reproducedbelow.

5.17 Abrasion Resistance (Plastics), Test No. 17

5.17.1 Purpose of Test

The purpose of this test is to determine whether the plastic has acertian minimum resistance to abrasion.

5.17.2 Procedure

5.17.2.1 Apparatus

(1) The apparatus for the abrasion shall be the Taber Abraser or itsequivalent. A load of 500 grams shall be employed on each wheel.

(3) An abrasive wheel meeting the following requirements at the time ofthe test shall be used:

(b) . . . The test shall be made with the pressure applied verticallyalong a diameter of the wheel, and reading taken 10 seconds after fullapplication of the pressure. Each wheel shall have a durometer hardnessof 72±5.

(4) The turntable of the Abraser shall rotate substantially in a planewith a deviation at the distance of 1/16 inch (1.59 mm) from itsperiphery of not greater than ±0.002 inch (±0.05 mm).

(5) An integrating sphere, photoelectric photometer constructedessentially as shown in FIGS. 5 or 6 and conforming to the requirementsshown below shall be used to measure the light scattered by the abradedtrack.

5.17.2.2 Test Specimens

(1) Three 4×4-inch (102×102-mm), flat specimens, as submitted, havingboth surfaces substantially plane and parallel, shall be tested.

5.17.2.3 Conditioning of Specimens

The specimens shall be conditioned prior to testing for a minimum timeof 48 hours at 71° F. to 75° F. (22° C. to 24° C.) and 50%±2% relativehumidity.

5.17.2.4 Method of Test

The test method shall be as follows:

(1) Level the Taber Abraser.

(2) . . . The load to be used is 500 grams on each wheel.

(4) Measure the initial haze of the specimen at a minimum of fourequally spaced points in the unabraded area in accordance with5.17.2.1(5)(m). The results shall be averaged for each specimen. In lieuof the four measurements, an average value may be obtained by rotatingthe specimen at three or more revolutions per second.

(5) The specimen shall be mounted on the specimen holder so that itrotates substantially in a plane and subjected to abrasion for 100cycles. Specimens shall be carefully wiped after abrasion with dry lenspaper (or its equivalent).

(6) Measure the light scattered by the abraded track at a minimum offour equally spaced points along the track.

The average initial haze determined by 5.17.2.4(4) shall be subtractedfrom the average total light scattered as measured by 5.17.2.4(6), thedifference representing the light scatter resulting from abrading thespecimen.

5.17.3 Interpretation of Results

The arithmetic mean of the percentages of light scattered by the threespecimens as a result of abrasion shall not exceed 15.0%.*

The energy-absorbing properties of the present laminates can beevaluated according to Regulation R43, Test Nos. 4.2 (large ball test[2.26 kg]), and 4.3 (small ball test [227 g]), portions of which arereproduced below.

4.2. Ball-impact test--2.26 kg

4.2.1. Number of test pieces

Six square test pieces of 300±₀ ¹ mm side shall be subjected to testing.

4.2.2 Test method

4.2.2.1. The method shall be that described in annex 3, paragraph 2.2.[impact occurs on the plastic face of the bilayer]*

4.2.2.2. The height of drop (from the underface of the ball to the upperface of the test piece) shall be 4 m±₀ ²⁵ mm.

4.2.3. Interpretation of results

4.2.3.1. The ball-impact test shall be deemed to have given asatisfactory result if the ball does not pass through the glazing withinfive seconds after the moment of impact.

4.2.3.2. A set of test pieces submitted for approval shall be consideredsatisfactory from the point of view of mechanical strength if one of thefollowing two conditions is met; that is to say, if:

4.2.3.2.1. All the tests give a satisfactory result; or

4.2.3.2.2. One test having given an unsatisfactory result, a furtherseries of tests carried out on a new set of test pieces givessatisfactory results.

4.3. Ball-impact test--227 g.

4.3.2. Number of test pieces. Twenty square test pieces of 300±₀ ¹⁰ mmside, shall be subjected to testing.

4.3.3. Test method

4.3.3.1. The method used shall be that described in annex 3, paragraph2.1. [impact on glass side of bilayer laminate]*

Ten specimens shall be tested at a temperature of +40° C.±2° C. and thenat a temperature of -20° C.±2° C.

4.3.3.2. The height of drop for the various thickness categories and themass of the detached fragments are given in the table below:

    ______________________________________                                               +40° C.                                                                              -20° C.                                                             Maximum           Maximum                                   Thickness of      permitted         permitted                                 Test Piece                                                                             Height of                                                                              mass of the                                                                              Height of                                                                            mass of the                               mm       fall (m) fragments (g)                                                                            fall (m)                                                                             fragments (g)                             ______________________________________                                        e < 4.5  9        12         8.5    12                                        ______________________________________                                    

4.3.4. Interpretation of results

4.3.4.1. The ball-impact test shall be deemed to have given asatisfactory result if the ball does not pass through the glazing. Ifthe interlayer is not torn, the weight of fragments detached from theside of the glass opposite to the point of impact must not exceed theappropriate values specified in paragraph 4.3.3.2. above.

4.3.4.2. A set of test pieces submitted for approval shall be consideredsatisfactory from the point of view of mechanical strength if one of thefollowing two conditions is met; that is to say, if:

4.3.4.2.1. Not less than eight tests at each test temperature gives asatisfactory result; or

4.3.4.2.2. More than two tests at each test temperature having given anunsatisfactory result, a further series of tests carried out on a newset of test pieces gives satisfactory results.

Impact resistance may be evaluated also according to ANSI-Z26 Test No.26 (Large Ball Test), Test No. 12 (Small Ball Test) and Test No. 9 (7 ozDart Test), hereby incorporated by reference. Bilayer laminates of thepresent invention wherein the present preformed sheet comprises anadhesive ply of greater than about 0.4 mm thick, and preferably greaterthan about 0.5 mm thick, exhibit impact resistant properties whichcomply with the ECE R43 and ANSI-Z26 standards described above.

Examples of the compositions, preformed sheets, glazing laminates andmethods for the preparation thereof according to the present inventionare described below.

EXAMPLE 1

A multi-ply sheet including a layer of self-healing thermoset materialis prepared by casting, on a horizontal release-coated glass support, aliquid mixture comprising:

1000 g of a polyether prepared by the condensation of 1,2-propyleneoxide with 2,2-bis(hydroxymethyl)-1-butanol and having a free hydroxylcontent of about 10.5 to about 12 percent and a molecular weight ofabout 450;

10 g of a stabilizer;

0.5 g of dibutyl tin dilaurate;

1 g of a sheeting agent; and

1020 g of a biuret of 1,6-hexanediisocyanate having a free NCO contentof about 23.2 percent.

The cast liquid film forms a uniformly level layer 0.19 mm thick and isfully cured to a solid supported thermoset polyurethane by raising thetemperature of the film to about 120° C. for about 15 minutes. The curedthermoset polyurethane has self-healing properties.

An energy absorbing adhesive ply of polyurethane is formed on the solidsupported thermoset material by casting a 0.53 mm thick liquid filmcomprising a mixture of Components A, B, and C, described below.

    ______________________________________                                                            Equivalents                                                                   NCO   OH     Wt. %                                        ______________________________________                                        Component A:                                                                  urea modified monomer mixture of                                                                    1       --     --                                       3-isocyanato-3,5,5-trimethyl-                                                 cyclohexane isocyanate                                                        [NCO content is about 31.5% by weight]                                        Component B:                                                                  polytetramethyleneglycol, MW 1000*                                                                  --      0.37   --                                       1,4-butanediol        --      0.63   --                                       Component C:                                                                  dibutyl tin dilaurate --      --     0.02                                     sheeting agent        --      --     0.05                                     stabilizer            --      --     0.50                                     ______________________________________                                         *sold as Polymeg 1000 by the Quaker Oats Co.                             

The composition is degassed in vacuo, heated to a temperature of about40° C. and cast onto the supported thermoset solid film maintained at atemperature of about 40° C. The composition is cast using a casting headsuch as disclosed in French Patent No. 2,347,170. The composition isallowed to form a uniformly level liquid film on the horizontal support,after which the temperature of the level liquid film is raised within aperiod of time of less than a few minutes to about 120° C. andmaintained at about 120° C. for about 25 minutes. The resulting fullypolymerized two-ply polyurethane sheet is removed from the horizontalsupport and may be stored for later use or used immediately in themanufacture of a glazing laminate.

A glazing laminate prepared from the two-ply sheet of the presentexample is assembled by contacting a glass sheet (2.6 mm thick) with thesurface of the two-ply sheet opposite that of the thermoset self-healingsurface. The resulting assembly is subjected subjected to a prepessingstage by passing it between two calenderer rollers, for example, byusing the apparatus disclosed in U.S. Pat. No. 4,327,634. The prepessedlaminate is subjected to an autoclaving cycle comprising treating thelaminate at a temperature of about 135° C. and a pressure of about 10bars for about two hours. The properties of the resulting laminate arepresented in Table 1 below.

EXAMPLE 2

A multi-ply sheet having a 0.41 mm thick self-healing thermoset ply and0.29 mm thick energy-absorbing adhesive polyurethane ply is preparedaccording to the method and compositions described in Example 1 above.

A glazing laminate is manufactured from this sheet and the propertiesthereof presented in Table I below.

EXAMPLE 3

A multi-ply sheet having a 0.315 mm thick self-healing thermoset ply anda 0.415 mm thick energy-absorbing polyurethane ply is prepared accordingto the method and compositions described in Example 1 above.

A glazing laminate is manufactured from this sheet and the propertiesthereof presented in Table I below.

EXAMPLE 4

A multi-ply sheet having a 0.39 mm thick self-healing thermoset ply anda 0.39 mm energy-absorbing polyurethane ply is prepared according to themethod described in Example 1 above, except that the composition formingthe energy-absorbing polyurethane ply comprises a mixture of ComponentsA, B and C, described below.

    ______________________________________                                                            Equivalents                                                                   NCO   OH     Wt. %                                        ______________________________________                                        Component A:                                                                  urea modified monomer mixture of                                                                    1       --     --                                       3-isocyanato-3,5,5-trimethyl-                                                 cyclohexane isocyanate                                                        [NCO content is about 31.5% by weight]                                        Component B:                                                                  polytetramethyleneglycol, MW 1000*                                                                  --      0.35   --                                       1,4-butanediol        --      0.45   --                                       polycaprolactone triol**                                                                            --      0.20   --                                       Component C:                                                                  dibutyl tin dilaurate --      --     0.02                                     sheeting agent        --      --     0.05                                     stabilizer            --      --     0.50                                     ______________________________________                                         *sold as Polymeg 1000 by the Quaker Oats Co.                                  **sold as NIAX 301 by Union Carbide.                                     

A glazing laminate is manufactured from this sheet and the propertiesthereof presented in Table I below.

EXAMPLE 5

A multi-ply sheet having a 0.31 mm thick self-healing thermoset ply anda 0.48 mm thick overlying polyurethene ply is prepared according to themethod described in Example 1 above, except that the composition formingthe overlying polyurethane ply is described in Example 4, above.

A glazing laminate is manufactured from this sheet and the propertiesthereof presented in Table I below.

EXAMPLE 6

A multi-ply sheet having a 0.16 mm thick self-healing thermoset ply anda 0.66 mm thick energy-absorbing polyurethane ply is prepared accordingto the method described in Example 1 above, except that the compositionforming the energy-absorbing polyurethane ply comprises a mixture ofCoponents A, B and C, described below.

    ______________________________________                                                            Equivalents                                                                   NCO   OH     Wt. %                                        ______________________________________                                        Component A:                                                                  urea modified monomer mixture of                                                                    1       --     --                                       3-isocyanato-3,5,5-trimethylcyclo-                                                                  1       --     --                                       hexane isocyanate                                                             [NCO content is about 31.5% by weight]                                        Component B:                                                                  polytetramethyleneglycol, MW 1000*                                                                  --      0.35   --                                       1,4-butanediol        --      0.55   --                                       polycaprolactone triol**                                                                            --      0.10   --                                       Component C:                                                                  dibutyl tin dilaurate --      --     0.02                                     sheeting agent        --      --     0.05                                     stabilizer            --      --     0.50                                     ______________________________________                                         *sold as Polymeg 1000 by the Quaker Oats Co.                                  **sold as NIAX 301 by Union Carbide.                                     

A glazing laminate is manufactured from this sheet and the propertiesthereof presented in Table I below.

The following examples demonstrate the reduction in the energy-absorbingproperties per unit thickness of energy-absorbing polyurethane ply inbilayer laminates of the present invention which include externaladhesion promoters.

EXAMPLE 7

A multi-ply sheet having a 0.32 mm thick self-healing thermoset ply anda 0.42 mm thick energy-absorbing polyurethane ply is prepared accordingto the method, and using the compositions, described in Example 1 above.A glazing lamiante is prepared as described in Example 1 except that thesurface of the glass sheet to be contacted with the multi-ply sheet iscoated with a silane adhesion promoter. The properties of the resultinglaminate are presented in Table I below and show a marked decrease inenergy-absorbing properties in comparison to the laminate of comparableply thicknesses and identical compositions of Example 3 above.

EXAMPLE 8

A multi-ply sheet having a 0.46 mm thick self-healing thermoset ply anda 0.56 mm thick energy-absorbing polyurethane ply and glazing laminateprepared from said sheet are prepared as in Example 7, above, and theproperties thereof presented in Table I below. The greater than 1 mmthick sheet results in a laminate having acceptable energy-absorbingproperties despite a high adhesion value.

The following example demonstrates the marked reduction inenergy-absorbing properties of the present laminates which include anenergy-absorbing polyurethane ply prepared by solution casting.

EXAMPLE 9

A multi-ply sheet having a 0.19 mm thick self-healing thermoset ply anda 0.53 mm thick adhesive polyurethane ply is prepared according to themethod, and using the compositions, described in Example 1, above,except that the adhesive ply is formed by the successive casting andevaporation of a solution of polyurethane prepared by solutionpolymerization. The properties of the glazing laminate prepared fromthis sheet are described in Table I below.

Example 10

A multi-ply sheet having ply thicknesses of Example 1, above, isprepared according to the method, and using the composition of Example1, above, except that the overlying adhesive polyurethane ply ispolymerized at about 60° C. for about 20 hours. The properties of theglazing laminate prepared from this sheet are presented in Table 1below.

                                      TABLE I                                     __________________________________________________________________________                    IMPACT RESISTANCE                                                                             SCRATCH                                              ADHESIVE ECE R 43 TESTS  RESISTANCE                                                                            ABRASION                              EXAMPLE                                                                              STRENGTH       227 g ball                                                                              Erichsen                                                                              RESISTANCE                            NO.    (daN/5 cm)                                                                          (psi)                                                                            2.26 kg ball                                                                        -20° C.                                                                     +40° C.                                                                     (g)     (% haze)                              __________________________________________________________________________    1      10    11.4                                                                               8 m 11 m 13 m >20 g   <4%                                   2      10    11.4                                                                             3.5 m  9 m  9 m "       "                                     3      10    11.4                                                                             4.5 m 10 m 13 m "       "                                     4       4     4.6                                                                               3 m  8 m  8 m "       "                                     5       3     3.4                                                                             4.5 m 10 m 12 m "       "                                     6       3     3.4                                                                               9 m 13 m 13 m "       "                                     7      20    22.8                                                                             3.5 m --   --   "       "                                     8      20    22.8                                                                               8 m 11.5 m                                                                             13 m "       "                                     9       8      9.1                                                                            3.5 m  4 m  3 m "       "                                     10     --    --   6 m  6 m 13.5 m                                                                             "       "                                     __________________________________________________________________________

Discussion of Laminate Properties

The glazing laminates of Examples 1 through 10 exhibit adhesive bondswhich are moisture resistant and do not delaminate, form bubbles orexhibit any irreversible defects after being subjected to thetemperature and humidity conditions of ANSI-Z26 Test Nos. 3 and 4. Theglazing laminates of the examples exhibit little or no change in theiradhesive strengths measured about 48 hours after the completion of thetests.

All of the laminates exhibit scratch resistant properties of greaterthan 20 g, as measured by the Erichsen apparatus, and possess an exposedply of self-healing material in which deformations disappear within lessthan about 10 minutes.

The laminates of Examples 1, 3, 5, 6 and 8 have energy-absorbingproperties which comply with the requirements of ANSI-Z26 Test Nos. 9,17 and 26 and ECE Regulation No. 43 Test Nos. 4.2 and 4.3. Examples 2,3, 4 and 5 demonstrate the thickness variable affecting theenergy-absorbing properties of a bilayer glazing laminate. Examples 2and 3 utilize the identical energy-absorbing polyurethane but differ inthe thickness of the ply: the ply of Example 2 is 0.29 mm thick and doesnot comply with the R-43 standards, while the ply of Example 3 is 0.42mm thick and passes the R-43 tests. A similar comparison is possiblebetween Examples 4 and 5 where an increase in energy absorber plythickness from 0.39 mm to 0.48 mm results in a laminate passing the R-43impact tests.

Examples 7 and 8 demonstrate the adhesive variable affecting theenergy-absorbing properties of the present laminate. The higher adhesivestrength possessed by the laminate of Example 7 results in a reductionin impact resistance. Example 8 shows that a thicker energy-absorbinglayer can result in adequate energy-absorbing properties despite a highadhesive value.

The adhesive ply in Example 9 is formed by solution polymerization andcasting and does not exhibit energy-absorbing properties sufficient tocomply with the R-43 standard at a ply thickness of 0.53 mm.

The adhesive ply in Example 10 is formed by polymerization at 60° C. for20 hours and does not possess the desired low temperatureimpact-resistant properties required to pass the R-43 standard.

The sheets and laminates of Examples 1 to 10 have the optical propertiesrequired for their use in automotive safety glass in compliance withANSI-Z26 standards. The sheets and laminates of Examples 1, 3, 5, 6 and8 comply with ANSI-Z26 Tests 1 to 4, 9, 12, 15 to 19, 24, 26 and 28 asmodified by Safety Standard No. 205, Glazing Materials [49 CFR 571.205,S.5.1.2.3, as amended Nov. 16, 1983], and therefore may be used invehicle safety windshields in the United States.

We claim:
 1. A preformed flexible multi-ply transparent sheet effectivefor use in a bilayer glazing laminate, having optical,moisture-resistant, and energy-absorbing properties effective for use ina bilayer glazing laminate, one ply of which comprises a self-healingthermoset polymeric material, the other ply of which comprises anenergy-abosrbing polyurethane ply which is substantially non-tacky atroom temperature but which is capable of itself being adhesive under theinfluence of heat and pressure, wherein said sheet is capable ofmaintaining, in the absence of an adhesion promoter, effective adhesionas measured by the temperature and moisture conditions of ANSI-Z26 TestNos. 3 and 4, said energy-absorbing polyurethane being prepared byreactive casting a solvent-free mixture of monomers; and wherein saidmulti-ply transparent sheet is produced by:(1) depositing on ahorizontal support a liquid film comprising a solvent-free mixture ofmonomers capable of forming a thermoset polymeric material; (2) forminga solid underlying film of said thermoset polymeric material bypolymerizing the monomers while on said support; (3) depositing on saidsupported underlying film a liquid film comprising:(a) an aliphatic or acycloaliphatic diisocyanate containing about 2 to about 10 wt. % of ureagroups, (b) a polyol component including(i) about 30 to about 45 OHequivalent percent of a polymeric diol having a molecular weight ofabout 500 to about 3,000, (ii) about 20 to about 70 OH equivalentpercent of a chain extender diol having a molecular weight of less thanabout 300, and (iii) about 0 to about 35 OH equivalent percent of apolyol having a OH functionality greater than 2; and (c) a polyurethanecatalyst, wherein the NCO/OH ratio of said mixture is about 0.8:1 toabout 1:1; (4) forming a solid, optical, energy-absorbing overlyingpolyurethane ply within about an hour, thereby forming said multi-plysheets; and (5) removing said multi-ply sheet from said support.
 2. Amulti-ply preformed sheet according to claim 1 wherein saidenergy-absorbing polyurethane ply has an initial tear strength at 20° C.greater than or equal to about 90 daN/cm; an elongation to rupture at20° C. of about 250 to about 500%; a tensile strength at break at 40° C.of greater than or equal to about 200 daN/cm² ; and a tensile strengthat 10% elongation at -20° C. of less than or equal to about 300 daN/cm².3. A multi-ply preformed sheet according to claim 1 wherein said mixtureof monomers capable of forming said energy-absorbing polyurethaneincludes a diisocyanate monomer component comprising a urea-containingdiisocyanate monomer and a diisocyanate monomer.
 4. The multi-plypreformed sheet according to claim 1 wherein said polyol monomercomponent comprises a mixture of polymeric diol and chain extender diolin a molar ratio of about 0.3:1 to about 1:1.
 5. The multi-ply preformedsheet according to claim 4 wherein said molar ratio of polymeric diol tochain extender diol is about 0.5:1 to about 0.8:1.
 6. The multi-plypreformed sheet according to claim 4 wherein said polyol mixtureincludes a triol monomer and the mole ratio of said polymeric diol tosaid triol is about 1.5:1 to about 4:1.
 7. The multi-ply preformed sheetaccording to claim 1 wherein said polyisocyanate component includesisophorone diisocyanate and the urea adduct of about 2 moles ofisophorone diisocyanate and about one mole of water, and wherein saidpolymeric diol is a polyether diol.
 8. The preformed sheet according toclaim 7 wherein said urea adduct comprises N,N'-bis(isophoroneisocyanate)urea.
 9. The preformed sheet according to claim 8wherein:said polymeric diol is polytetramethylene glycol having a MW ofabout 1000; said chain extender diol is 1,4-butanediol; and said polyolhaving an OH functionality greter than two is polycaprolactone triol.10. The glazing laminate comprising a multi-ply preformed sheetaccording to claim 1 adhered to a glass or plastic ply wherein theadhesion between said preformed sheet and said ply is greater than about2 daN/5 cm and less than about 15 daN/5 cm.
 11. The glazing laminateaccording to claim 10 wherein said ply of energy-absorbing polyurethaneis greater than or about 0.4 mm thick.
 12. The glazing laminateaccording to claim 11, wherein said sheet is a bilayer sheet having saidenergy-absorbing polyurethane sheet adhered to a glass ply.
 13. Abilayer glazing laminate which exhibits optical, energy-absorbing,moisture resistant, and abrasion resistant properties required by ANSIZ26, Test Nos. 1-4, 9, 12, 15-19, 24, 26 and 28, comprising a multi-plypreformed sheet according to claim 1 adhered to a glass or plastic ply.14. The preformed flexible multi-ply transparent sheet according toclaim 1, wherein said energy-absorbing polyurethane is prepared byreactive casting a solvent-free mixture of monomers, wherein said polyolcomponents includes about 0.05 to about 35 OH equivalent percent of apolyol having a OH functionality greater than
 2. 15. The preformedflexible multi-ply transparent sheet according to claim 1, wherein saidaliphatic or cycloaliphatic diisocyanate of said liquid film containsabout 5 to about 7% by weight of urea groups.
 16. The preformed flexiblemulti-ply transparent sheet according to claim 15, wherein saiddiisocyanate containing urea groups is a urea-modified isophoronediisocyanate comprising a mixture of isophorone diisocyanate andN,N-bis(isophorane isocyanato) urea.
 17. A bilayer glazing laminatecomprising the multi-ply preformed sheet according to claim 1, adheredto a glass ply.
 18. The glazing laminate according to claim 17, which isa safety windshield.